Statistical Mechanics
The distribution of eccentricities in random regular graphs
Dor Lev-Ari, Ofer Biham and Eytan Katzav
We derive a closed-form analytical expression for the distribution of eccentricities (DoE) in random regular graphs (RRGs) that consist of $N$ nodes of degree $c$. The DoE is given by the tail distribution $P(E > \ell) \simeq 1 - \exp \left[ - \exp \left( - \frac{ e^{b \ell} - \mu }{\beta} \right) \right]$, where the distance $\ell$ takes integer values, $b = \ln (c-1)$ is the shape parameter, $\beta = \frac{c-2}{c} N$ is the scale parameter and $\mu = \frac{c-2}{c} N \ln N$ is the location parameter. By providing the full distribution rather than a single characteristic length scale, we present a detailed view of the large-scale structure. In spite of the fact that the degrees of all the nodes are the same, their eccentricities exhibit non-trivial variations. We derive a closed-form expression for the mean eccentricity, which is given by $\langle E \rangle \simeq \frac{\ln N}{\ln (c-1)} + \frac{\ln \ln N}{\ln (c-1)} - \frac{ \ln c - \ln (c-2) }{ \ln (c-1) } + \frac{1}{2}$. We calculate the mode of the DoE, which exhibits a staircase profile as a function of the network size. Interestingly, the mode is given by $E_{\rm mode} ={\rm Round} \left( \langle E \rangle \right)$, where ${\rm Round}( x )$ is the nearest integer to $x$. We also calculate the variance ${\rm Var}(E)$ and show that it exhibits oscillations as a function of the network size $N$. The results presented in this paper may serve as
benchmarks for algorithmic approaches to eccentricity calculations in large sparse networks. The eccentricities are important in practical applications such as broadcasting and global dissemination, where the network performance is determined by the longest delay times.
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Quantum Physics
Robustness of periodicity in Grover walks under a magnetic vector potential
Hiroto Sekido and Etsuo Segawa
We study the effect of
magnetic vector potentials on periodic Grover walks on finite graphs. The
magnetic vector potential is introduced through the framework of
quantum graphs, which induces the Grover walk as a special case. We regard the
magnetic vector potential as a perturbation of a periodic Grover walk and investigate the robustness of its periodicity. Our analysis reveals that the response to such perturbations depends on the spectral structure of the underlying graph. In particular, when the graph possesses at least one non-simple
eigenvalue, we derive a Hermitian
matrix that characterizes the robustness of its periodicity. As a consequence, for initial states orthogonal to the eigenspaces of the unperturbed Grover walk corresponding to the
eigenvalues $\pm1$, we show that the perturbed dynamics is asymptotically described by a continuous-time
quantum walk generated by this Hermitian
matrix.
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Fluid Dynamics
Exploring 2D turbulent properties in anisotropic and disordered Fourier space: Insights into inverse cascades and universal superdiffusion from randomly sampled triadic interaction
Francesco Carbone and Sergio Servidio
Two-dimensional turbulent properties are investigated within a “low-density” Galerkin-truncated system, with a focus on both Eulerian and Lagrangian characteristics. In particular, an ordered pseudo-logarithmic and a disordered distribution of {active (i.e. resonant)} triads has been sampled in
Fourier space, allowing for a tunable degree of anisotropy and “triadic density”, enabling investigation into their effects on the inverse energy cascade and particle pairs
diffusion. Despite the non-uniform and anisotropic mesh in the
Fourier space, this reduced model successfully captures 2D
turbulence scaling laws and maintains integral energy cascade properties. It consistently reveals the classical double-cascade: a $k^{-5/3}$ inverse cascade at large scales and a $k^{-3}$ direct cascade at small scales, observed across all configurations. Furthermore, while anisotropy, controlled via angular sampling, significantly impacts the vorticity field organization and the efficiency of the inverse energy flux, the system's diffusive properties exhibit a Richardson superdiffusive scaling, $\ell^2(t)\sim t^3$, for particle pair separation. The prescribed spectral anisotropy affects the Lagrangian eddy diffusivity, enhancing
diffusion along one direction for short timescales. Conversely, for longer times, particles become uncorrelated, and the separation distance degenerates into the classical Brownian scaling, $\ell^2(t)\sim t$. The observed $t^3$ pair-dispersion indicates that the retained spectral interactions sustain super-ballistic separation, while anisotropy mainly affects the dispersion amplitude without modifying the scaling.
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Materials Science
Computing binary alloy phase diagrams with explicit configurational and vibrational entropy
Sarath Menon, Marvin Poul, Tilmann Hickel et al. (+2 more)
Phase stability in multicomponent solid solutions depends on configurational
entropy beyond the ideal mixing limit, but capturing it together with vibrational
entropy within the same atomistic framework remains challenging. Here, we extend non-
equilibrium thermodynamic integration to composition-dependent transformations through an alchemical interpolation of the interactions, combined with Monte Carlo identity exchange moves and molecular dynamics that sample the vibrational and non-ideal configurational
entropy along the integration path. We apply the framework to the Au-Cu binary
alloy using Atomic Cluster Expansion (ACE) potentials trained on density functional theory data using the LDA, PBE, and r2SCAN functionals, and construct composition-temperature phase diagrams directly from atomistic free energies. We find that explicit configurational sampling lowers the AuCu order-disorder transition temperature predicted by an ACE potential trained on LDA data by about 126 K, closer to the experimental value of 683 K, and substantially widens the stability range of the solid solution. At the same time, the much larger sensitivity to the exchange-correlation functional shows that this level of agreement should not be interpreted as general predictive accuracy. No single functional is uniformly accurate across the thermodynamic observables considered here, showing that functional sensitivity must be assessed alongside configurational effects when constructing atomistic phase diagrams.
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All authors Sarath Menon, Marvin Poul, Tilmann Hickel, Jörg Neugebauer, Ralf Drautz
Solar and Stellar Astrophysics
Search for double-line spectroscopic binaries in RAVE survey
Mikhail Kovalev
I present a study for double-line spectroscopic binaries content in RAVE DR6 spectra, using composite spectral model. Three complementing selections found 2813 composite spectra, belonging to 2605 unique targets. Also these results were compared with automatic classification based on t-SNE map, which shows good agreement. Additionally I identified several spectra affected by problems with wavelength calibration.
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High Energy Physics (Experiment)
Track fitting at the full LHC collision rate
Pierre Billoir, Thomas Boettcher, Michel De Cian et al. (+1 more)
The LHCb experiment at the Large
Hadron Collider underwent a major upgrade before the LHC Run 3 data taking period, employing an all-software approach in its trigger system. Here we present a fast implementation of a Kalman filter, used in the first trigger stage since the 2025 data taking period, allowing to determine parameter estimates of charged-particle trajectories at the full LHCb collision frequency of 30 MHz. This approach replaces computationally expensive
magnetic field map lookups and numerical integration methods with fast analytical parameterisations while maintaining the mathematical framework of Kalman filtering. Implemented on approximately 500 GPUs within the first-level trigger, the
algorithm has replaced the previous partial track fitting
algorithm in the real-time trigger environment at the cost of a 2% increase in processing time. Compared to the previous fitter this parameterised Kalman filter shows a significantly improved momentum resolution, resulting in a factor of two improvement in the invariant mass resolutions for reconstructed D0 and J/{\psi}
hadrons. It additionally demonstrates greater robustness against detector misalignment effects and substantially sharpens the discrimination between genuine particle trajectories and accidental background, more than doubling the rejection of the latter at no cost to genuine-track efficiency, for a standard selection working point.
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All authors Pierre Billoir, Thomas Boettcher, Michel De Cian, Lennart H. Uecker
Cosmology and Nongalactic Astrophysics
Probing Graviton Mass with MeerKAT PTA and SKA-PTA Forecasts
Zhi-Chao Zhao and Sai Wang
In this study, we derive constraints on the graviton mass using the 4.5-year data release from the MeerKAT
Pulsar Timing Array (MPTA) and provide forecasts for the upcoming Square Kilometre Array PTA (SKA-PTA). By modeling the modified dispersion relation and the corresponding tensor correlation function for massive gravitons, we perform
Bayesian inference on the angular-correlation measurements under three noise configurations. Our 90% credible upper limits on the graviton mass span $m_g < (2.10$-$2.58) \times 10^{-23}\,\mathrm{eV}/c^{2}$. Including monopolar and dipolar contributions does not significantly alter these bounds, confirming that the constraints are driven by the quadrupolar tensor correlation. All results remain fully consistent with general relativity. For SKA-PTA, we forecast sensitivities down to $m_g \sim 10^{-24}\,\mathrm{eV}/c^{2}$ with a 10-year observing baseline and $m_g \sim 10^{-25}\,\mathrm{eV}/c^{2}$ with a 50-year observing baseline, representing order-of-magnitude improvements over current limits. This work demonstrates the power of current and future PTA observations to test fundamental aspects of
gravity in the nanohertz band.
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Earth and Planetary Astrophysics
Dust Growth in Binary Systems: Inhibition of dust settling and growth in circumbinary discs
Antoine Alaguero, Nicolás Cuello, Jean-François Gonzalez et al. (+4 more)
Stellar multiplicity alters the density structure of protoplanetary discs and thereby the initial conditions for
planet formation. Yet, the interplay between companion-disc interactions and
dust growth remains poorly understood. The goal of this work is to investigate to what extent the density structure of a disc undergoing
tidal interactions with a companion
star promotes or inhibits the growth of
dust grains. We perform a set of hydrodynamical simulations of protoplanetary discs orbiting one or both
stars of a binary, including
dust growth and fragmentation. We explore a range of companion orbits and compare the results with a single-
star reference case. We find that
dust growth is mainly driven by local accumulations of
dust. In circumbinary discs, the maximum grain size is up to five times smaller than in isolated discs. This result likely originates from the perturbations caused by the inner binary, which prevent
dust grains from properly settling and drifting. As a consequence, the conditions required to trigger strong clumping driven by the streaming instability are difficult to achieve. In contrast, circumstellar discs in binary systems exhibit grain sizes similar to those in isolated discs, leading to comparable conditions for strong clumping by the streaming instability.
Planet formation through core
accretion seems challenging in circumbinary discs harbouring binaries larger than a few au, suggesting that circumbinary
planets observed near the dynamical stability limit did not form in situ. Conversely, perturbations from external companions only marginally affect density-driven
dust growth compared to isolated systems.
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All authors Antoine Alaguero, Nicolás Cuello, Jean-François Gonzalez, Daniel J. Price, Maxime Lombart, Jeremy L. Smallwood, Philippe Thébault
Data Analysis and Statistics
Inferring Non-Normal Amplification Geometry from Multivariate Time Series
V.R. Saiprasad, V. Troude and D. Sornette
Across hydrodynamics, ecology, neuroscience, network dynamics, non-Hermitian physics, and socio-economic systems, asymptotically stable dynamics can exhibit large transient amplifications that are invisible to
eigenvalue-based analyses. The mechanism is
geometric rather than spectral: perturbations entering along one direction may be expressed transiently along another, allowing asymptotic decay to coexist with strong transient or noise-driven amplification. We introduce non-normal directional response inference, a data-driven method for detecting this geometry from multivariate time series when the governing operator is unknown. A local linear operator is estimated from sliding windows and projected onto the dominant two-dimensional input-response subspace. The reduced dynamics are summarized by the
eigenvalue splitting $\Delta$, eigenvector non-orthogonality $K$, and the scale-free ratio $R=K/K_c(\Delta)$, where $K_c(\Delta)$ is the two-dimensional threshold for transient amplification. Controlled
benchmarks show that the reduced geometry, particularly $R$, can be recovered from finite data even when the full high-dimensional operator is poorly estimated. Tests across sample size, dimension, training horizon, spectral structure, and non-stationarity confirm that the relevant response geometry requires far fewer observations than full-
matrix recovery. Applied in moving windows to electrohysterogram, seizure
EEG, freezing-of-gait, and unstable push-up inertial recordings, the method reveals systematic changes around known physiological or behavioral episodes through shifts in $R$, changes in $\Delta$, or stronger projection of fluctuations onto the inferred response direction. It thus exposes interpretable changes in local response geometry without framing the problem as supervised event detection.
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Astrophysics of Galaxies
Enabling Cosmic Web Analysis at Gigaparsec Scales: A Multi Block Approach for DisPerSE
Ankit Singh, Frazer Pearce, Meghan Gray et al. (+1 more)
Cosmic filaments are the longest structures in the Universe and the dominant element of the
cosmic web, channelling matter onto clusters and shaping the environments in which
galaxies form and evolve. Accurate reconstructions of this network across gigaparsec volumes are increasingly important for cosmology and
galaxy evolution. However, the most commonly used topological filament finder, DisPerSE (Discrete Persistent Structures Extractor), faces a
memory bottleneck: it requires a Delaunay tessellation of the full input point set, preventing application to large simulations. Naively splitting the volume fails, as different sub-volumes yield inconsistent tessellations and filament networks. We present a frozen-core method that overcomes this bottleneck while preserving the global
topology. The volume is decomposed into overlapping blocks whose tessellations are filtered by a circumsphere criterion retaining only globally valid tetrahedra; a post-processing pipeline merges the tiled outputs through core filtering, deduplication, and boundary stitching. Validation against a monolithic reference on a $300\,h^{-1}\,\mathrm{Mpc}$ MDPL2 subvolume shows 99.6% total length recovery, 100% recovery of density maxima and minima, and 94.7% individual filament matching (the ${\sim}$5% of unmatched filaments are predominantly short, low-significance structures). We apply the method to the full $(1\,h^{-1}\,\mathrm{Gpc})^3$ MDPL2 box (92 million
haloes), producing a gigaparsec-scale filament catalogue. As a first application, we measure the connectivity ($\kappa$) for 22,900
haloes spanning $M_{200\mathrm{c}} = 10^{12}$-$10^{15.5}\,h^{-1}\,\mathrm{M}_\odot$, finding a power-law mass-connectivity relation that extends from group to cluster scales, providing the first confirmation in an $N$-body
halo catalogue that the theoretically predicted scaling holds across three decades in
halo mass.
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All authors Ankit Singh, Frazer Pearce, Meghan Gray, Gustavo Yepes
Physics and Society
Photovoltaics beyond the panel: system-level net energy under grid and firming constraints
Hans Peter Beck
Photovoltaics can exhibit favourable installation-level energy return on investment (EROI), yet electricity must also be delivered when
solar and wind generation are insufficient. This study evaluates how the energy balance changes when the boundary is expanded to reliable electricity supply. A fleet-equivalent
benchmark model includes component turnover, grids, storage, renewable overbuild, dispatchable backup, and fuel supply. It is not a simulation, optimization, or real-system prediction. Photovoltaics provide the accounting reference in an illustrative Central European mix of 80% wind and 20% photovoltaics, while the firming penalties arise more generally from weather-dependent generation. Expanding the boundary is decisive. The unfirmed renewable fleet retains an EROI of 10.7-16.0, but does not provide continuous electricity. Battery load-balancing references decline from 7.1-12.5 for 1h to 0.7-2.3 for 24h. Seasonal hydrogen yields 3.4-7.7; adding a 1h battery reduces the combined range to 2.9-6.8. Pipeline-gas and LNG backup yield only 1.2-2.6 and 1.0-2.2. The lifecycle-carbon advantage narrows accordingly. Under present industrial supply chains, GWP$_{100}$ intensities rise from 38-75 gCO$_2$eq/kWh without firming to 80-289 gCO$_2$eq/kWh for hydrogen and battery-hydrogen firming, and 121-327 gCO$_2$eq/kWh for gas backup. These favourable
benchmarks set orientation, site, curtailment, and delivery factors to unity; real deployment lowers EROI and raises emissions. The results identify firming as a critical energetic constraint: reliable decarbonization requires firm low-carbon generation with sufficient net-energy surplus to sustain a resilient industrial society.
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Optics
Ultraviolet direct absorption microscopy for single particle protein/nucleic acid quantification
C. J. Richards, D. van de Lockand, D. Wolters et al. (+1 more)
Bio-nanoparticles are pivotal to next generation nanotherapeutics, but providing single-particle biomolecular characterization remains a crucial challenge. Herein we present ultra-violet direct absorption microscopy (UV-DAM) to tackle this challenge. UV-DAM is based on a tailored illumination scheme for absorption-only imaging, combined with a custom deep UV light source. Combined, they provide biomolecular specificity with single particle sensitivity. As such, UV-DAM provides rapid, label-free, high resolution, biochemical imaging. Enabled by these capabilities, we implement the classic nucleic acid:
protein absorption assay at the single virus level where we demonstrate UV-DAM's ability to distinguish empty from DNA-loaded viral capsids based on bimolecularly specific absorption fingerprints. UV-DAM presents the translation from bulk UV-visible spectrometry to single-particle assessment, a crucial advancement for nanomedicine characterization where particle loading efficiencies are often heterogenous. Beyond this, UV-DAM is applicable to a wide range of nanomaterials or investigation of biological process with high spatio-temporal resolution and intrinsic molecular contrast.
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All authors C. J. Richards, D. van de Lockand, D. Wolters, M. Liebel
Nuclear Theory
Responses of multiparticle observables to multidimensional nuclear deformation in relativistic heavy-ion collisions
Ying Shan Zhao and Yifeng Sun
Relativistic heavy-ion collisions provide a unique opportunity to probe ground-state
nuclear structure through its imprint on the initial collision geometry. We investigate how multiparticle observables respond to combined variations of quadrupole deformation, triaxiality, and hexadecapole deformation, using $^{129}$Xe+$^{129}$Xe collisions as a representative testing ground. We perform a joint analysis in the three-dimensional $(\beta_2,\gamma,\beta_4)$ parameter space and construct initial-state
estimators for several flow and mean transverse momentum correlation observables. At the initial-state level, $\rho_2$ is primarily sensitive to $\beta_2$ and $\gamma$, with its sensitivity to $\gamma$ enhanced at nonzero $\beta_2$. The nonlinear response coefficient $\chi_{4,22}$ is predominantly sensitive to $\beta_4$, while its dependence on $\beta_2$ and $\gamma$ remains comparatively weak. Higher-order correlators exhibit more complex multidimensional response patterns; in particular, $\rho_{224}$ shows a dependence on $\gamma$ and $\beta_4$ that becomes more pronounced at finite $\beta_2$. We further employ the iEBE-VISHNU hybrid model to examine whether these deformation sensitivities survive the subsequent dynamical
evolution. The final-state calculations indicate that the sensitivity of $\rho_2$ to $\beta_2$ and $\gamma$ is largely preserved, whereas the $\beta_4$ sensitivity of $\chi_{4,22}$ is substantially reduced. For the other higher-order observables, the initial-state sensitivities are modified by the
evolution or cannot be resolved with the present statistics.
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Instrumentation and Methods for Astrophysics
DUET: Design of a simultaneous InGaAs–CCD split-beam imager for ultra-cool dwarf exoplanet transit survey
Peter P. Pedersen, Clark Baker, Karolina Dziewiecka et al. (+4 more)
We present the design of DUET, a dual-channel imager being built for the SPECULOOS-Southern Observatory (SSO) to detect and characterise transiting terrestrial
exoplanets orbiting ultra-cool
dwarfs. A dichroic beamsplitter at 955\,nm directs visible light to a deeply-depleted silicon CCD and near-infrared light to a CMOS-based InGaAs detector, enabling fully simultaneous photometry with bandpasses from 0.4 to 1.7\,\textmu m. The near-infrared filters have been chosen to suppress sensitivity to atmospheric precipitable water vapour (PWV) variability, a dominant source of correlated noise in ground-based infrared photometry of cool
stars. We describe the optical and mechanical architecture, the dichroic and filter selection, the choice of detectors, and the control system.
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All authors Peter P. Pedersen, Clark Baker, Karolina Dziewiecka, Mathias Beck, Michaël Gillon, Amaury H.M.J. Triaud, Didier Queloz
Optics
Empirical verification of principal mode orthogonality and relative phase calibration in photonic lanterns
Adam K. Taras, Barnaby R. M. Norris, Christopher Betters et al. (+6 more)
Photonic lanterns efficiently map input spatial modes to single-mode outputs for applications like high angular resolution imaging and nulling interferometry. However, manufacturing limits prevent full control over the device's mode transfer
matrix at the design stage, making empirical characterisation essential. In this work we further analyse a
dataset of direct measurements of a photonic lantern's principal modes using digital off-axis holography over a 73 nm range near 1550 nm. By analysing the electric field directly, we find that the principal modes are significantly more orthogonal than random vectors in a space of the same size, as expected for near-adiabatic devices. We propose metrics for quantifying this effect, noting that mode converters with orthogonal principal modes provide better conditioned inverse solvers. We also simulate additional measurements that characterisation systems could take, where the orthogonality would be leveraged to determine the relative phase between principal modes.
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All authors Adam K. Taras, Barnaby R. M. Norris, Christopher Betters, Daniel S. Dahl, Nathan Long, Andrew Ross-Adams, Peter G. Tuthill, Jin Wei, Sergio Leon-Saval
Strongly Correlated Electrons
Emergence of a monopole phase in the $J_1{-}J_2$ Heisenberg model on the triangular lattice for small magnetic fields
Sasank Budaraju, Shi Feng, Josef Willsher et al. (+3 more)
We investigate the ground-state phase diagram of the $J_1{-}J_2$ Heisenberg model on the triangular
lattice under an external Zeeman field $H$ by using the variational Monte Carlo approach. We span a region with $0 \le J_2/J_1 \le 0.2$ and $0 \le H/J_1 \le 2$, to assess the fate of the (putative)
spin-
liquid phase that has been detected for $J_2/J_1=1/8$ at zero
magnetic field. Simple variational ansatze are proposed for a few candidate states, and their energetics are compared on large clusters to obtain the phase diagram. For $J_2/J_1 \lesssim 1/6$, a continuous transition from a gapless "Y” phase to a gapped "up-up-down” phase is obtained, as predicted by
spin-wave theory. Most importantly, around $J_2/J_1=1/8$, a condensate of monopoles (which are gapless gauge excitations of the
spin liquid at $H=0$) is stabilized in a significant region of the phase diagram, for small Zeeman fields. Here, a finite scalar chirality is present, while no transverse
magnetic order is detected. The stability of the monopole phase is confirmed by a field-theory approach that includes a self-consistent random-phase approximation of the low-lying
spin fluctuations. The boundary between the monopole and "Y” phases is also obtained with no free parameters.
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All authors Sasank Budaraju, Shi Feng, Josef Willsher, Johannes Knolle, Frank Pollmann, Federico Becca
Materials Science
Boson peak and medium-range elastic heterogeneity in calcium silicate hydrate probed by terahertz spectroscopy and low-temperature calorimetry
Xiangyu Li, Ying Chen, Jipeng Luo et al. (+9 more)
The
boson peak (BP), a universal vibrational anomaly of disordered solids, has been predicted but not systematically characterized in calcium silicate hydrate (C-S-H), the binding phase of hardened cement. Building on a preliminary terahertz survey, we characterize the BP across five Ca/Si ratios (0.5-1.7) using terahertz time-domain spectroscopy (THz-TDS) and low-temperature calorimetry, two probes of vibrational dynamics that complement the static picture of conventional structural methods. After Bruggeman correction for crystalline
impurities, both probes locate the BP near 1 THz; they agree on frequency but diverge in intensity. The terahertz integrated spectral weight and the calorimetric Cp/T3 peak both fall monotonically with Ca/Si, whereas the apparent terahertz peak height is maximal at Ca/Si = 1.0, where damping is low and oscillator strength still substantial. This decoupling marks a structural crossover between silicate-chain depolymerization and interlayer calcium filling. From the BP we obtain a medium-range dynamical correlation length of order 1 nm (0.3-2 nm) and a coherent-potential elastic-heterogeneity parameter that decreases from gamma = 0.98 to 0.48 as Ca/Si rises; the Debye-normalized BP frequency (nu_BP/nu_D = 0.15-0.17) places C-S-H within the range reported for silicate glasses. Because gamma governs the distribution of energy barriers for local structural rearrangements, it provides a quantitative, composition-resolved descriptor relevant to the intrinsic creep and thermal transport of C-S-H, linking nanoscale vibrational dynamics to the macroscopic durability of concrete. The dual-probe
boson-peak approach is transferable to other amorphous solids, including the supplementary cementitious materials of low-carbon cements.
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All authors Xiangyu Li, Ying Chen, Jipeng Luo, Ya Chen, Linhao Wang, Lidan Tian, Gan Ding, Zeyu Lu, Zhangli Hu, Biqin Dong, Yue Li, Zongjin Li
Chaotic Dynamics
Bayesian Basin Tracking: Efficient Global Continuation of Multistable Dynamical Systems
Pedro Haerter, Alexandre Wagemakers, Alvar Daza et al. (+1 more)
Mapping the global phase space of high-dimensional multistable dynamical systems is computationally prohibitive because conventional approaches require extensive numerical integration. Here, we introduce
Bayesian Basin Tracking (BBT), an adaptive
Bayesian framework that exploits the persistence of basin boundaries under parameter continuation to reconstruct global phase-space structure using only a fraction of the simulations required by conventional methods. By modeling the probability that a sampled initial condition converges to a particular attractor, the method represents the phase-space geometry established at a given parameter value through a Dirichlet-multinomial model. At a nearby parameter value, these probabilities are estimated by updating the prior distribution with newly sampled data. To detect boundary crises and bifurcations autonomously, we use the log Bayes factor as an information-theoretic sensor that triggers dense resampling only when structural changes render the historical prior statistically implausible. We validate the framework using the discrete Hénon map, the continuous-time Duffing oscillator, and a 300-dimensional network of coupled Rössler oscillators. BBT overcomes the restrictive dimensional scaling of deterministic grid tessellations by concentrating the most computationally demanding calculations in structurally volatile regions. In high-dimensional synchronization landscapes, it achieves an almost sixfold computational speed-up while retaining theoretically derived error bounds.
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All authors Pedro Haerter, Alexandre Wagemakers, Alvar Daza, Miguel A.F. Sanjuán
Optics
Motion-Based Self-Normalisation Enables Precision Nanoparticle Sizing
D-Dré K.J.M.J. Braam, Daan Wolters and Matz Liebel
Label-free all-optical nanosizing based on interferometric or darkfield-imaging infers particle size, composition, or shape from single-particle scattering signals. These signals are, however, scaled by a spatially varying normalisation profile that combines the non-uniform illumination with position-dependent detection and data-processing effects. Common normalisation strategies estimate this profile from a direct measurement of the illumination field or background. This is not possible in background-free geometries, such as side- or light-sheet-type illumination, where the illumination does not reach the detector. Here we introduce a self-normalisation method that reconstructs the normalisation profile from the scattering signals of freely diffusing nanoparticles, without additional hardware or calibration samples. To remove the bias caused by particle-to-particle heterogeneity, single-particle trajectories are normalised against each other in regions of spatial overlap, where distinct particles sample the same normalisation profile. In a transmission geometry, the reconstructed profile agrees qualitatively with a direct illumination measurement and reduces signal variations within single trajectories from 6.5% to 2.0% (one sigma), corresponding to a diameter uncertainty of about 0.7%. Under 90-degree side-illumination, where the illumination field cannot be measured through the detection path, normalisation with the reconstructed 3D profile reduces within-trajectory signal variations from about 30% to 4-10% across most of the sampled volume. As the method solely relies on the scattering signal already acquired, our approach is directly compatible with existing interferometric and darkfield nanoscopy platforms and extendable to other scattering or fluorescent modalities, including light-sheet microscopy.
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Optics
Local Variance-Based Calibration of Programmable Photonic Interferometer Meshes
Gökhan Elmas, Igor A. Litvin and Janis Nötzel
Programmable photonic interferometer meshes enable reconfigurable linear optical transformations, but their performance depends critically on accurate calibration of Mach-Zehnder interferometers and phase shifters. Conventional methods often require node isolation, dedicated routing paths, orthogonal training states, reference channels, or prior phase-voltage characterization, which become increasingly difficult in large thermally tuned meshes. We introduce a local variance-based self-calibration method using intensity-only measurements. Controlled phase perturbations are applied, and calibration points are identified from minima of the measured output-power variance. For Mach-Zehnder interferometers, the variance follows a characteristic |sin(theta)| dependence, allowing bar and cross operating points to be found without conventional node isolation. For phase shifters, balanced interference produces a complementary |cos(phi)| variance signature, enabling quadrature calibration through the same statistical principle. We validate the method experimentally on an 8 x 8 silicon nitride programmable photonic processor using a fully automated two-stage procedure. Starting from random phase settings, all Mach-Zehnder interferometers are calibrated first, followed by phase-shifter calibration under balanced-interference conditions. As a system-level test, we implement an embedded 4 x 4 Hadamard transformation on the 8 x 8 processor using a Clements decomposition. These results establish local output variance as a simple calibration observable for programmable photonic meshes. The method is compatible with discrete random phase ensembles and requires neither conventional node isolation nor orthogonal training fields, making it a practical calibration primitive for scalable self-stabilizing photonic processors.
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Astrophysics of Galaxies
The Mysterious Case of Iron in XMPs: Anomalous High log(Fe/O) Observed in Extremely Metal-Poor Galaxies HSCJ1631+4426 and SDSSJ0811+4730
Aaron Myszka, Themiya Nanayakkara, Karl Glazebrook et al. (+8 more)
We present integral field spectroscopic observations of two local extremely metal-poor
galaxies (XMPs), HSCJ1631+4426 and SDSSJ0811+4730, obtained with the Keck
Cosmic Web Imager (KCWI) over the wavelength range $3545-5529$ Å at a spectral sampling of 0.5 Å, capturing bright nebular emission lines essential for determining gas-phase
metallicity and chemical enrichment measurements. Using integrated spectra, we derive oxygen abundances of $\rm12+\log(O/H)=7.079\pm0.010$ and $6.926\pm0.004$, and elevated Fe/O ratios of $\rm\log(Fe/O)=-1.57\pm0.17$ and $-1.28\pm0.07$, for HSCJ1631+4426 and SDSSJ0811+4730 respectively. Each
galaxy is fully contained within the $\sim$8” field of view, with 0.15” spaxels providing spatially resolved information. These measurements indicate unusually efficient iron enhancement at extremely low
metallicity; Fe/O ratios approach or exceed
solar despite oxygen abundances of only $\sim$2%
solar, inconsistent with enrichment from core-collapse
supernovae alone or delayed Type Ia
supernovae given the young ages of the systems. Comparison with chemical
evolution models suggests rare, highly energetic explosions such as bright hypernovae and/or pair-instability
supernovae are likely responsible. Our results reinforce the growing evidence that XMPs can reflect the nucleosynthetic processes of early energetic
stellar explosions, serving as local laboratories for chemical enrichment pathways prevalent in the early Universe.
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All authors Aaron Myszka, Themiya Nanayakkara, Karl Glazebrook, Sarah M. Sweet, Brent Groves, Nikole M. Nielsen, Jarle Brinchmann, Yuki Isobe, Chiaki Kobayashi, Haruka Kusakabe, Michael V. Maseda
Quantum Physics
Moment Optimization in the Navascués-Pironio-Acín Hierarchy
Francesco Flora, Losel Matos, Tim Heightman et al. (+3 more)
The Navascués-Pironio-Acín (NPA) hierarchy provides a convergent sequence of semidefinite programming (SDP) relaxations for noncommutative
polynomial optimisation, ubiquitous in
quantum physics. However, its practical applicability is limited by the combinatorial growth in operator moments required at each level. Since not all moments contribute equally to bound tightness, selecting moments within a fixed computational budget is a relevant problem. We reframe moment selection as combinatorial subset selection and show it is governed by strong higher-order synergistic interactions among moments, quantified through a marginal synergy diagnostic adapted from complex systems theory. We develop and compare three optimisation methods: Parallel Tempering (PT), an RBM-based reinforcement learning policy, and
Bayesian Optimisation (BO). On the $I_{3322}$ Bell inequality
benchmark, all three substantially outperform greedy approaches at costs around two orders of magnitude below brute force, with the RBM achieving the closest approach to optimal throughout the hard transition regime. We apply the framework to the 174 Bell inequalities in the $(4,4,2,2)$ scenario, finding heterogeneous convergence behaviour across inequalities, and to the one-dimensional Heisenberg
spin chain, demonstrating that physically motivated monomial bases are internally compressible and are not globally optimal in general. A budget-aware search over a broader pool improves certified bounds on long-range correlations by nearly two orders of magnitude. These results establish a scalable framework for moment selection in noncommutative
polynomial optimisation, with broad applications across
quantum physics and
quantum information.
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All authors Francesco Flora, Losel Matos, Tim Heightman, Tamás Kriváchy, Adan Garriga, Antonio Acín
Mathematical Physics
Polar Form of the Dirac Operator in Low-Dimensional Space-Times
Luca Fabbri and Giuseppe De Maria
We express in polar form the Dirac operator as left-multiplication by an assigned
matrix: we use this technique to find its right-resolvent for low-dimensional spaces.
Optics
3D scanning microscopy through scattering surfaces using the optical memory effect
Harish Sasikumar, Gerwin Osnabrugge, Kirsten Gerritsma et al. (+2 more)
Wavefront shaping allows light to be focused through scattering objects. However, the wavefront correction found is only valid in a small region called the isoplanatic patch. Here we present a simple approach to extend this isoplanatic patch by shifting and scaling the corrected wavefront appropriately, demonstrating an 8.6-fold increase in the lateral scanning range and a 1.5-fold increase in the axial range through a scattering layer without the need to perform additional wavefront shaping measurements. Our findings agree well with a simple geometrical model that also allows us to extract the effective position of the scattering layer from the measurements.
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All authors Harish Sasikumar, Gerwin Osnabrugge, Kirsten Gerritsma, Bahareh Mastiani, Ivo M. Vellekoop
General Relativity and Quantum Cosmology
Orbital Dynamics and Gravitational-Wave Signatures of EMRIs in Self-Dual Loop Quantum Gravity Black Holes
Yu Wang, Meilin Liu and Haiguang Xu
Loop
quantum gravity (LQG) predicts
quantum modifications to classical black-hole spacetimes, which may leave imprints on the dynamics and gravitational-wave signals of compact objects in the strong-field regime. In this work, we investigate the orbital dynamics and gravitational-wave signatures of extreme mass-ratio inspirals (EMRIs) in a self-dual loop
quantum gravity black hole spacetime. We analyze test-particle motion in the static, spherically symmetric self-dual LQG geometry characterized by two
quantum parameters: the polymeric parameter $P$ and the minimal area parameter $a_0$. The effective potential and orbital structure are systematically studied, and we quantify the influence of
quantum corrections on circular-orbit stability and strong-field orbital behavior. Compared with the classical Schwarzschild spacetime, LQG corrections modify the near-horizon orbital dynamics. Based on the orbital
evolution, we construct gravitational-wave waveforms and investigate the impact of
quantum corrections on waveform morphology. We find that LQG effects accumulate during the long inspiral phase, leading to noticeable signal deviations from the classical case. To incorporate rotation, we construct a rotating extension of the self-dual spacetime using the Newman–Janis
algorithm. The resulting LQG-corrected Kerr geometry is used to analyze orbital motion, revealing the interplay between
spin and
quantum corrections in strong-field trajectories. Finally, we perform a Fisher
matrix analysis to estimate potential constraints on
quantum parameters from future space-based gravitational-wave detectors. Our results indicate that EMRI observations provide a promising avenue to probe
quantum gravitational effects in black-hole spacetimes.
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General Relativity and Quantum Cosmology
Warped Spacelike Singularities and the $C^0$-Inextendibility of Birmingham-Kottler Spacetimes
Bobby EkaGunara
We establish a local obstruction to continuous Lorentzian extensions at a class of warped spacelike singularities. The criterion is expressed through two integrability conditions, a monotonicity condition on the relative warp factors, and divergence of the longitudinal factor; it does not require any
symmetry of the closed fiber. The main
geometric step is a radial compression of terminal causal traces, which replaces the rotational deformation available in spherical
symmetry. The compression yields a compact chronological separator in an adapted boundary chart. Longitudinal translations then produce radial-slice distances that diverge intrinsically while remaining uniformly controlled in the extension chart. Next, we construct the canonical one-horizon Birmingham-Kottler spacetime in global Kruskal coordinates and classify all finite proper-time ends of its timelike geodesics. Every boundary-approaching finite maximizer supplied by a putative extension is thereby forced to the singular end. The local obstruction and the geodesic classification imply $C^0$-inextendibility for the one-horizon Birmingham-Kottler family with nonpositive cosmological constant and every closed connected fiber satisfying $\text{Ric}_{\gamma_\Sigma}=(n-2)k\gamma_\Sigma$, without assumptions of homogeneity, orientability, or simple connectivity.
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Chaotic Dynamics · Cross-listed from eess.SP
Quantifying the complexity of trajectory ensembles with clustering-weighted multivariate multiscale sample entropy
Chenxiao Tian and J/"urgen Hackl
Across the physical and life sciences, data increasingly appear as ensembles of trajectories, from chaotic flows and satellite constellations to clinical cohorts. Established sample-
entropy measures characterize individual time series, while averaging across an ensemble discards population structure and cannot distinguish redundancy from diversity. We introduce clustering-weighted multivariate multiscale sample
entropy (CWMMSE), which groups trajectories into behavioral patterns and weights each by its dynamical complexity. CWMMSE is a weighted
entropy of the population's pattern distribution. Its empirical plug-in
estimator is strongly consistent for a fixed finite partition, and it separates two components that can diverge in real data: individual complexity and population diversity. Both are essential. Averaging ignores diversity, whereas spread alone can mistake a varied but predictable population for a complex one. Across eleven physical, environmental, engineering, and biomedical systems, CWMMSE ranks a calm ocean region above an energetic but individually more complex one, identifies a major earthquake as a collapse in system complexity, and reverses the conclusion from averaging in cardiac cohorts, where disease reduces population diversity. Supported by an open, reproducible implementation, these results show that population complexity should be measured rather than averaged.
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Materials Science
Tunable Magneto-Excitonic Coupling in Alloyed van der Waals Antiferromagnet
Maciej Smiertka, Oliwia Janikowska, Katarzyna Olkowska-Pucko et al. (+18 more)
The unique coupling between
magnetic order and photo-generated
excitons, electron-hole pairs bound by Coulomb interaction, in layered
magnetic semiconductors offers a powerful mechanism for controlling light-matter interactions. In the van der Waals antiferromagnet CrSBr, this coupling is exceptionally strong and manifests distinctly between two coexisting excitonic states: the localised, Frenkel-like XA
exciton and the more delocalised, Wannier-Mott-like XB
exciton, providing a unique playground for the optical control of magnetism. Here, we reveal how chlorine incorporation reshapes the magneto-optical interplay in CrSBr1-xClx by simultaneously modifying its electronic structure, excitonic properties, and
magnetic interactions. Combining magneto-optical spectroscopy up to 85 T with state-of-the-art quasiparticle self-consistent GW (QSGW) calculations on
alloy supercells, we show that Cl insertion progressively localises the excitonic wavefunctions and drives both states toward a more Frenkel-like regime. This
evolution is accompanied by a systematic reduction of the
magnetic-field-induced energy renormalisation, most prominently for the XB
exciton. Our work connects
exciton character directly to magneto-excitonic coupling. Furthermore, it establishes compositional alloying as an effective strategy for engineering the coupling between
magnetic and optical properties in van der Waals
magnetic semiconductors.
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All authors Maciej Smiertka, Oliwia Janikowska, Katarzyna Olkowska-Pucko, Grzegorz Krasucki, Katarzyna Posmyk, Paulina Peksa, Alessandro Surrente, Dimitar Pashov, Kseniia Mosina, Zdenek Sofer, Mark van Schilfgaarde, Adam Babinski, Maciej R. Molas, Gabriela Komorowska, Esteban Zamora-Amo, Andres Castellanos-Gomez, Federico Mompean, Mar Garcia-Hernandez, Michal Baranowski, Swagata Acharya, Paulina Plochocka
Plasma Physics
Computational studies of giant edge islands and unpaired X-points in HSX and W7-X by manipulating coil currents
Robert Davies, Dieter Boeyaert, Alexis Wolfmeister et al. (+5 more)
We present
magnetic configurations in the Helically Symmetric eXperiment (HSX) and Wendelstein 7-X (W7-X), in which the edge
magnetic structure exhibits island chains which are spatially larger than the previously reported configurations. These “
giant" island chains (with rotational transform $\iota=4/3$ or $4/4$ for HSX and $\iota=5/6$, $5/5$ or $5/4$ for W7-X) are obtained by reducing the coil current in main coil 6 for HSX and non-planar coil 5 for W7-X (i.e. the coil nearest the up-down symmetric cross-section $\phi=36^\circ$ for W7-X and $\phi=45^\circ$ for HSX). This appears a sufficient (but not necessary) condition for
giant islands. The
giant islands create X-point legs which transport
plasma to the
plasma-facing components (PFCs). In the most extreme cases, the island O-points leave the domain of the field line map and the divertor legs of the remaining “unpaired" X-points do not close around the island. We show for W7-X, via the construction of quadratic flux-minimising surfaces, that these island size trends can mostly be interpreted as changes in magnitude of a resonant perturbation on a changing resonant “unperturbed"
magnetic surface. We use the anisotropic heat
diffusion code EMC3-Lite to find “
giant island" W7-X configurations which are promising for PFC heat loads. These configurations significantly degrade the neoclassical transport performance but allow exploration of novel divertor regimes; for example, we show that the internal island pitch can be increased. This leads to favourable downstream/upstream
plasma density ratios according to simple models; an attractive finding which motivates further investigation.
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All authors Robert Davies, Dieter Boeyaert, Alexis Wolfmeister, Benedikt Geiger, Georg Harrer, Joachim Geiger, Louis Day, Lucas Sanchez-Garay
Soft Condensed Matter
Amoeboid swimming of active vesicles
Reiner Kree and Annette Zippelius
We investigate the shape dynamics and migration of weakly deflated active vesicles driven by processes acting either directly in the membrane or transmitted by the cytoskeleton. For a force-free vesicle, local membrane incompressibility suppresses rigid-body translation, so that migration arises from time-dependent shape deformations. Assuming small excess area enables a systematic analysis of the coupled deformation and migration dynamics in free space, i.e. in the absence of substrate adhesion or confinement. Depending on the strength and frequency of the activity, the vesicle exhibits several dynamical regimes, including synchronized oscillations, quasiperiodic shape changes, transitions between non-propelling and propelling states, and intermittent motion.
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